Need 4340 or 300M Input shaft for C6?

78 bronco, 4700-5000 lbs, 300 ft sand drag truck/occasional street driver, getting a 552 BBF with something like 700hp and 725+ ft/lbs. Needs to hold up to a trans brake, even though most of the time I will be foot braking it.
Is an upgraded input shaft necessary here and if so, where do you guys get yours from? Will obviously be real easy to do when I have everything out.

I ran a stock one for a long time and never broke one, 5000lbs with a brake, A head 598.

Last time trans was freshened we put a good one in for piece of mind but i don't recall the brand.

PM J.Toney on here and he can tell you what brand, probably any of the aftermarket ones will do the trick.

Frank suggests over 800 ftlb to upgrade . I've used a few TCI ones been ok

Damn these c6’s are pretty tough! I’ll leave it alone for now, thanks guys!

Fordaholic495 wrote:Damn these c6’s are pretty tough! I’ll leave it alone for now, thanks guys!

I'm guessing on sand ? traction is limited ? I'd say the stock input will do ok:)

Paddle tires hook up better than you would think but for the most part yes, just spinning.

I bought one from ati you have to call them it isn't in the catalog it is the 300m material .The only broken c-6 input shaft I have seen was out of my 66 comet street car .Probably metal fatigue .Doug

I bought a 300m shafts from Broader. 3 years ago it was $175.

PATC 300M C6 INPUT SHAFT

PA FROM SUMMIT C6 INPUT FROM SUMMIT

TCI TCI C6 INPUT SHAFT

HUGHES @ JEGS 4340 C6 INPUT

NA or power adder? IMO, you'll probably get along fine with stock shaft at the NA level. But I might add it for a buffer if extra power shows up one day. I and Norm had gotten by with factory shafts in very similar apps for many seasons. Personal stuff was 521"/700h/650tq/5k with small plate kit, on transbrake, using smallish 17 paddle Hookers.
I will be upping power soon, and a upgrade shaft will be going in.

I've gotten them from Transtar, not sure who they use.  Norm's was a few years back, can't recall for sure where it was sourced.  All I've used seem to fit and hold well.  But prefer TCS Arizona if possible, TCS Canada is a great product also.

Just remember also to check which you have . There are two types , a 31/31(early) & a 31/30 (later)

Converter ends are same , it's the forward drum end is different